"Density and Social Life" Quality and Density PPT Courseware

Description

"Density and Social Life" Quality and Density PPT Courseware

situational experience

Question 1: At room temperature, blow up two equal-sized balloons, put one into hot water and the other into cold water. After a while, take out the two balloons. Which balloon is larger?

Question 2: When the same volume of water and salt water are put into the exact same beaker, how to distinguish the two liquids?

learning target

1. Know the effect of temperature on density.

2. Know the important role of density in production and life, and be able to explain simple issues related to density and social life.

3. Understand that density is a characteristic of matter, and be able to use density knowledge to identify matter.

Self-learning

Read pages 120-122 of the textbook and complete the independent learning questions.

1. Density and social life

Density is the basic property of matter. Each substance has its own density. Density has important value in our social life.

2. Density and temperature

1. The formation of wind in nature

The air expands in volume due to heating and becomes less dense and rises. After the hot air rises, cold air flows from all directions, forming wind.

2. Utilization of wind

People can use wind power to collect water, irrigate, grind flour, propel sailing boats, etc. In modern times, large-scale use of wind power is mainly for power generation.

The air expands in volume due to heating and becomes less dense and rises. After the hot air rises, the cold air above flows from all directions, forming wind.

People can use wind power to collect water, irrigate, grind flour, propel sailing boats, etc. In modern times, large-scale use of wind power is mainly for power generation.

Self-study test

Effect of temperature on density: Temperature ______ changes the density of a substance. Among our common substances, _____ has the most significant thermal expansion and contraction, and its density is also most affected by _____. Generally, the density of _____ and _____ is less affected by temperature.

abnormal expansion of water

1) Abnormal expansion of water: At 4oC, the density of water is _____.

When the temperature is higher than 4oC, as the temperature increases, the density of water ________; when the temperature is lower than 4oC, as the temperature decreases, the density of water ________.

2) Characteristics: When water solidifies into ice, its volume is ____ and its density is ____.

Identify substances; milk; wine; high strength; low density; solid; high density.

[Guess] Iron.

Cooperation and exchange

1. Light the candle and you will see the fan blades rotate. Because after the candle is lit, the temperature of the air above increases, the volume expands, and the density becomes smaller. The hot air with lower density rises, forming convection, which causes the fan blades to rotate.

2. When water freezes, its mass remains unchanged and its density decreases, making it easy for the bottle to burst.

3. In general, the density of gases, liquids, and solids decreases as the temperature increases;

The density of gases is greatly affected by temperature, while the density of solids and liquids is less affected by temperature.

4. No matter whether the temperature of 4oC water increases or decreases, the volume increases and the density decreases. It is not as dense as the water at 4oC, so the water at 4oC is always at the bottom of the lake.

Applications of density in life

1. Use density to identify substances;

2. Identifying the concentration of milk and wine in business, and the problem of preparing salt water and selecting seeds in agricultural production;

3. Choose different materials based on density knowledge: (1) Cars and airplanes often use high-strength, low-density materials (alloy materials, fiberglass); (2) Low-density foam plastics are often used as fillers in product packaging, which are shock-proof and Easy to transport and low price. (3) When filming movies and TV series, use low-density materials as props instead of heavy objects.

4. In winter, the heater in the room is usually installed under the window, and in summer, the air conditioner in the room is usually installed above the window.

Compliance testing

1. A bottle can hold 1kg of water. This bottle can hold 1kg of water ( )

A.Gasoline B.Alcohol C.Mercury D.Salt water

2. Two balls A and B have the same volume but different materials. When 2 balls A are placed on the left plate of the balance and 3 balls B are placed on the right plate, the balance is balanced, then the two balls A and B ( )

A. Mass ratio 2:3 B. Volume ratio 2:3

C. Density ratio 2:3 D. Density ratio 3:2

3. After a certain mass of water freezes, then ( )

A. The density is reduced by 1/10 B. The density is reduced by 1/9

C. The volume increased by 1/10 D. The volume increased by 1/9

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Update Time: 2024-07-06

This template belongs to Physics courseware Lu Jiao edition eighth grade physics volume 1 industry PPT template

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